The invention relates to a transmission unit, particularly a multi-range transmission.
Transmission arrangements in the form of power branched transmissions in the form of superposition gears are known in a plurality of models. To illustrate, reference is made to the following publications:                1. EP 1 333 194        2. DE 197 55 612 A1        3. EP 1 061 287 A2        4. DE 43 08 761 A1        5. DE 887 457 C        6. DE 10 2004 022 204 B3        
The model according to the publication DE 197 55 612 A1 comprises a transmission input shaft, a continuously variable transmission drive in the form of a traction drive coupled to the transmission output shaft, said transmission drive exhibiting an input and an output, wherein the input is non-rotatably connected to the transmission input shaft, a fixed transmission step as well as a superposition gear with a first input step, said input step being non-rotatably connected to the output of the continuously variable transmission drive. Further a second input step is provided which optionally by means of a first clutch can be connected to the transmission input shaft via the fixed transmission step and an output step, which is non-rotatably coupled to the transmission output shaft. In this connection the fixed transmission step is on the drive side non-rotatably coupled to the transmission input shaft and with respect to the fixed transmission step on the output side the first clutch is arranged in such a way that said clutch optionally connects the second input step of the superposition gear on the output side to the fixed transmission drive.
The continuously variable transmission is directly coupled to the transmission input and with this the drive shaft and hence also to the speed of the drive machine. A relief of the superposition gear in a range of higher speeds of the output shaft or of lower transmission ratios of the continuously variable transmission drive is achieved due to the fact that a second coupling is provided which optionally connects the first input step to the output step of the superposition gear. As a result a rigid connection between the output shaft of the continuously variable transmission drive and the output shaft is created, as a result of which the entire superposition gear is jumped in the torque flow. The continuously variable transmission drive can in dependence on its dimensioning only transfer a maximum permissible torque, otherwise in the case of very high loads impermissibly large slip states are to be observed, which lead to an increased wear on the traction mechanism. On the basis of the direct coupling of the continuously variable transmission to the transmission input said transmission input is however always subjected to the prevailing conditions on the transmission input. That means that the input of the CVT is impinged with the speed on the transmission input and with this of the drive machine.
From Publication EP 1 333 194 a transmission module is anticipated which with regard to its structure has been modified in such a way that the load of the traction drive could be considerably reduced and with this the transferability of higher performances via said traction drive could be ensured. In this model the transmission module is likewise constructed as a superposition gear unit. This comprises a transmission input and a transmission output, further two superposition gears arranged between the transmission input and transmission output and coupled with one another to a four-shaft planetary gear. Between the first superposition gear and the second superposition gear a continuously variable transmission is further interposed in the form of a traction drive. Each planetary gear comprises a sun gear, a ring gear, planetary gears and a planet carrier. The individual shafts in the process are formed by the sun gear, ring gear or planet carrier of the respective superposition gear. The transmission input is in the process non-rotatably connected to a first shaft of the first superposition gear and a first shaft of the second superposition gear. The transmission output is non-rotatably connected to a second shaft of the first superposition gear and a second shaft of the second superposition gear. The coupling of the two three-shaft planetary gears to a four-shaft planetary gear takes place in the process by coupling the first and second shafts of the first and second superposition gears. The individual shafts in the process assume the function of inputs and outputs depending on the operating state. Further means for the changing of the transmission ratio on the traction drive are provided. In the process one of the two superposition gears—first or second superposition gear—exhibits planetary gears combing with each other in pairs between the sun gear and ring gear. Said planetary gears are pivoted on the planet carrier. On the basis of this it is guaranteed for a sub-range of the total operating range that the CVT works at maximum rotational speed, wherein a switch with respect to the transmission ratio can also take place at the individual disks at maximum engine speed, that is a turning above zero is possible and hence with the inventive transmission along with a geared neutral also a change in the direction of rotation can be realized. The double-rotor design offers the advantage that in the case of an increase of the speed caused by them on the output coupled with the continuously variable transmission, in particular ring gear, this planetary gear brings about a reduction corresponding to the design of the other planetary gear on the output of the respective other planetary gear coupled with the continuously variable transmission, in particular the ring gear. However, according to this implementation it is not possible to have the continuously variable transmission work over the entire operating range many times at maximum rotational speed.
Another implementation of a multi-range transmission is anticipated from the publication DE 10 2004 022 204 B3. Said publication comprises only one simple planetary gear step, three spur wheel steps, two coupling units and one continuously variable transmission. The output shaft is optionally connected to the sun or gear ring shaft by means of the two coupling units.
The additional publications likewise disclose multi-range transmissions in which case two three-shaft planetary gear sets are combined into one four-shaft planetary gear set.